Revert 924ce2c5ba4d1c1dc781a6a06682204d358421bb

Because test-unit didn't provide the benchmark test. And This test
  is fragile with the several environments.

test/rubygems/test_gem_version.rb

@@ -2,8 +2,6 @@
 require 'rubygems/test_case'
 require "rubygems/version"
 
-require "minitest/benchmark"
-
 class TestGemVersion < Gem::TestCase
   class V < ::Gem::Version
   end
@@ -110,15 +108,6 @@ class TestGemVersion < Gem::TestCase
     end
   end
 
-  def bench_anchored_version_pattern
-    assert_performance_linear 0.5 do |count|
-      version_string = count.times.map {|i| "0" * i.succ }.join(".") << "."
-      version_string =~ Gem::Version::ANCHORED_VERSION_PATTERN
-    end
-  rescue RegexpError
-    skip "It fails to allocate the memory for regex pattern of Gem::Version::ANCHORED_VERSION_PATTERN"
-  end
-
   def test_empty_version
     ["", "   ", " "].each do |empty|
       assert_equal "0", Gem::Version.new(empty).version